This invention relates to tires and tire castings for vehicles and more particularly to tires of the type having one or more radial plies or the like together with circumferential belt reinforcements.
Vehicles tires having radial-ply reinforcements extending between the bead regions within the tire together with belts extending circumferentially within the tread region have recently come into widespread use. Both the radial plies and circumferential belts are typically formed of layers of cords of high tensile strength material such as steel cables, for example, with the cords being embedded in an elastomeric material to form the plies and belts. Relative to older forms of tire, the belted radial-ply configuration provides a highly reliable and durable tire and one which is more resistent to various forms of unwanted deformation during use. Reinforcements of this particular kind also serve to reduce the rate of tread wear and to protect against punctures and other problems encountered in tires.
Belted radial-ply tires as heretobefore constructed are subjected to another problem which to some extent detracts from the basic advantages discussed above. In particular, there is a tendency for a phenomenon known as belt separation to occur. The stresses and distortions to which a tire is subjected in use tend to break the bond between circumferential belts and the surrounding elastomeric tire material. While this can occur at any region on the belts it tends to be particularly pronounced along the edges of the belt.
Belt separation can be initiated by fatigue as well as high stressing and is accelerated by operating the tire at high internal temperature levels. The edges of the belts are particularly vulnerable to these types of failure due to the stress riser effect where the high-strength belt material terminates.
As heretofore constructed, the circumferential belt reinforcements have usually been situated radially outwardly from the radial ply or plies. Such an arrangement has certain advantages such as the fact that circumferential belts in this location serve to some extent to protect the underlying radial plies which are the primary reinforcement of the tire carcass. However, in such an arrangement there is nothing to resist belt separation other than the strength of the bond between the belts and the surrounding rubber or other elastomeric material.
There have been some tire configurations proposed for tires having a plurality of radial plies in which some of the circumferential belts have been situated radially inward from at least some of the radial plies. A belt which is situated radially inwardly from a radial ply may be to some extent more resistant against belt separation owing to the effect of the radial ply in resisting stresses and distortions of the kind which tend to aggravate the problem. As heretobefore constructed, these tire configurations have not realized the full potential of such a disposition of circumferential belts relative to radial plies. Belt separation has continued to be one of the more serious problems encountered in the use of this otherwise highly advantageous type of tire.